Spark Plug Heat Range And Gap For 30-32 PSI

[Scoobum]

I'm ordering the ignition upgrade kit from John at Caspers. I ran AC 43's at .030 last year at 25 PSI for the 6.7 run. Should I go to 42's for the higher boost level...likely 30-32 PSI. There's lots of high gear fuel in the chip and I'll be using C16...so I'm not worried about detonation. Reading tells me the heavy hitters are tightening the spark plug gaps down to .024 for 35 PSI blasts. What's the consensus?

[williambavila]

I was ol by dusty to tighten my gap to 24 to try and isolate a issue. That did not help. I suggest staying at .030 or .032 as that is what I am going back to. I prefer autolite 24's because the threads go all the way down the plug unlike the  ac's. Nothing against the ac's

[good2win22]

My reading indicates that a R42T gapped at .025 works well with iron heads at that boost level.  You running the TA heads?

[Steve Wood]

for normal boosts of 25-28, I have found no improvement going below 0.032".  I have run 0.035" at 30 psi a few times.

I wonder if people tighten the gap because they need to, or they have encountered a miss?

In other words, where does the folk lore hit the highway

[williambavila]

I would listen to the old fart. I am running stock heads with autolite 24s gapped at 30-32 now.

[earlbrown]

With some personal first hand experience with ACs the last few years, the first thing I was do is toss those things.

NGK and Autolite still seems to make a fine plug.

[good2win22]

I haven't been to that amount of boost your asking about. I run the 43's gapped at .032 and haven't seen any issues on stock heads.  I am just back at work and sitting in front of the computer again all day.  You asked a question, so I started researching.  Perhaps I'll put up a disclaimer in my signature that reads, "unless I specifically tell you that I have done something, then it's all speculation."

[Steve Wood]

every time I have had an ignition problem, I have had a miss.  The more boost I ran, the worst the miss became and I never had a problem knowing the car was missing.  I really don't understand why one would tighten the gap to see if the car has an ignition problem when it is not missing under boost.

[Scoobum]

Thanks for the responses guys...always appreciated. Earl, I've run AC's exclusively... and have never had an issue...but I swap new ones in twice a season. I think the ones I run are CR 43 TS. Jason, I'm running the same engine as last year with the 8445's. I sold the TA's yesterday.

[Steve Wood]

they started making autolites overseas, I understand.  I have seen a couple of bad ones.   Beginning to think the NGK's might be the most reliable.  Not sure they are being counterfeited, but?

[earlbrown]

Thanks for the responses guys...always appreciated. Earl, I've run AC's exclusively... and have never had an issue...but I swap new ones in twice a season. I think the ones I run are CR 43 TS. Jason, I'm running the same engine as last year with the 8445's. I sold the TA's yesterday.

I read a post on the other boards about ACs having a problem (and really not believing them to much).  The one dude mentioned he maintains a fleet of cars and shit starting going weird....   tossing the AC's fixed the problem.

At that same timeframe I noticed my slant 6 '72 van and my Blazer starting acting up  with the same plugs.    I asked my boy at the parts store (the one that lets me get away with warranting plugs when they get old) if he's heard feedback about the Delcos...

...his response got me to switch to plugs other than the Delcos.   Gas mileage went up on all my N/A cars and my GN quit acting like I needed a new ignition module.



Results my vary/contents may settle from shipping/ and I will never buy AC plugs again.    Much like womens that show they aren't worth messing with, I'm out.

[Steve Wood]

I think there are a lot of phony AC's on the market.

[motorhead]

The only reason to close the gap is IF the spark is being "blown out" by the cylinder pressure.  In many cases a weak signal to the plug is the issue, not the gap at the plug itself.  The newer COP systems are great for getting the most power across the gap.  It is interesting to note that waste spark systems tend to wear plugs out quicker, so finding a quality copper (or some space age voodoo material) plug is preferred. 

http://www.ngksparkplugs.com/pdf/DYK/DYK_Waste%20Spark%20Ignitions.pdf

Get NGKs, run the largest gap you can, and change/re-gap them often.

[nocooler]

Brad - I always ran 42's in my car, 43's were too hot, i wouldn't get KR but it'd break up at high boost with alky - you could tell it wasn't happy.


NGK is the plug of choice for me - they are easy to read and seem to be the highest quality copper on the market. I buy them in bulk from rock auto, they are cheaper than anyone. Shipping might kill you.

If I'm going to spray the car gets a fresh set every time out, and I change out my hot cylinders before a pass, and read them after. Depending how they look I'll change the tuneup accordingly and after a few passes I'll change all of them out.

[TexasT]

Part # on the ngk?
Mostly stock here. Do the numbers go colder like autolite and ac?